This invention relates to ordinance devices. More specifically, this invention relates to the conversion of hot gases produced from burning propellant into electrical energy for use in weapons such as bombs, artillery projectiles and the like.
Electrical energy in a round has always been at a premium. Thermal batteries, piezoelectric elements and mercury cells have been the principal sources of electrical power in large caliber munitions. In thermal batteries, where the voltage output depends on the number of cells used, a considerable volume of space must be taken up for devices requiring a high voltage level or a long operating time. Mercury cells must be stacked to obtain appropriate voltage levels adding weight and increasing the volume of needed space. Piezoelectric elements have been placed in the nose of an ogive to produce electrical energy upon impact of the warhead. However, piezoelectric elements located in the nose offer only a limited area of impact, and the voltage output is a function of the impact angle, falling off as the angle increases.
This produced energy is allowed to pass through a detonator. The detonator is comprised of a thin wire surrounded by a sensitive explosive, such as lead-azide. Current passing through a wire heats the wire and causes the lead-azide to explode. Explosion of the lead-azide causes the main explosive charge in the warhead to detonate.
In the case of the piezoelectric elements, electrical energy is produced by pressure. As the element upon impact is compressed along a certain axis, an electrical charge is generated. This charge is then passed through the detonator causing it to explode and initiate the explosive in the warhead.
In the case of the thermal battery, the electrical energy is produced by set-back forces which are generated when the round is fired. A fuzed salt is released on set-back, which subsequently causes an electrical charge to be generated between two electrodes, similar in process to the lead storage battery. This charge is then stored in a capacitor and used to set off the detonator upon impact of the warhead.
In small caliber munitions (20 mm to 40 mm) electrical energy is virtually non existent. Some rounds incorporate piezo-electric elements similar in operation to those used in large caliber munitions. Most rounds, however, incorporate a point detonating type fuze and rely on the round's impact on target to initiate the warhead's explosive train. A spring-loaded pin is driven into the detonator with sufficient force to cause detonation. This type of initiating system reduces the warhead's functioning sensitivity when the warhead impacts at large oblique angles.
Also used in small caliber munitions is the "spitter" point detonator fuze which is a small shaped charge located in front of the ogive. On impact, the spitter shaped charge is activated and a stream of particles is projected from the front of the ogive back into a tube at the apex of the shaped charge, and subsequently causes the explosive at the top of the tube to detonate.
These prior art devices have been found to contain the following disadvantages:
1. In large caliber munitions, thermal batteries and mercury cells require a considerable volume of space, necessitating minimization of the amount of high explosive for a given warhead size.
2. In large caliber munitions, thermal batteries and mercury cells increase the weight of the warhead, necessitating an increase in the amount of propellant needed to maintain projectile velocity.
3. In small caliber munitions, electrical energy is virtually non-existent. Consequently, electronic timing fuzes cannot be used.
4. Piezo-elements in the nose of the ogive offer only a limited area of impact on the ogive where the fuze can cause the warhead to function. Electro-optical fuzing systems, which possess greater graze functioning sensitivity with negligible increase in weight and volume, cannot be used in small caliber munitions without availability of electrical energy.
5. When spit-back fuzes are used, the material in the fuze sits in the path of the jet, and the activation of the spitter causes some damage to the warhead.
Accordingly, it is a primary object of this invention to provide the necessary electrical energy to operate any electronic devices in the round, as well as to insure the initiation of the warhead's explosive train, without the use of thermal batteries or mercury cells. Integrated with a compatible impact sensor, such as a triboluminescent sensor or a double walled ogive switch, the thermoelectric power supply could supply the required power in the fuze system to initiate the warhead's explosive train.
A still further object of this invention is to provide a considerable saving in weight and volume when utilizing this power supply. Any guidance or timing devices could be integrated into a single monolithic chip and could receive the necessary power to operate from the thermoelectric power supply.
Yet another object of this invention is to make electrical energy available in small caliber munitions. These rounds can, with this invention, incorporate electronic timing fuzes or electro-optical fuzing systems with negligible increase in weight and volume. With the removal of the point detonating type fuze, rounds such as the M552 which utilize shape charge liners will be made more effective, since the jet which is formed will no longer have to pass through the fuze debris.
A further object of this invention is that high explosive dual purpose rounds utilizing shallow cone shape charges can be developed for use in the newer gun systems having higher velocities and spin rates.